Do you know the parts of the eye? If not, this lesson will help you to identify the parts of the eye and understand their specific functions. After learning about the eye, you will be able to test your knowledge with a quiz.
What is the Eye?
Is the eye a round, liquid-filled sphere that allows us to see? Well, essentially yes, but it is much more complicated than that. There are many parts that must work together to allow mammals to see.
There are two regions of the eye: the front and the back. We’ll discuss the front of the eye first.
The Front of the Eye
The front part of the eye is what you see if you stand in front of a mirror. It consists of the:
The iris is the colored part of the eye.
It is important because it controls the size of the pupil. The pupil is the dark circle inside the center of the eye. The dark hole is altered in shape by the iris, affecting the amount of light that is let into the eye. The pupil is large when light is low or it is dark outside and tiny when it is very sunny or bright.The cornea is the clear covering over the pupil and iris. This is the reason that contacts are dome shaped because they sit on the cornea.
The cornea provides 66% of the optic power that the overall eye has. This means that the cornea is very important in focusing what we see by bending light.The sclera is the white part of the eye that we see in the mirror that becomes pink or red when we are tired or have sneezed so hard that our eyes become bloodshot. This eye part is the protective, outer layer of the eye. It is made up of elastic-like fibers called elastin and collagen, a common connective tissue found in mammals.The eyeball is held in place by the eyelid, which is the first protective layer.
The eyelid has an inner layer of skin called conjunctiva. The conjunctiva covers the sclera and provides mucus and tears for eye lubrication and bacterial infection prevention. It does not cover the cornea.
The Back of the Eye
In the back of the eye, are the important items that we cannot see when we look in the mirror. This area consists of the:
- Optic nerve
These parts have important independent functions.
The lens of the eye works in conjunction with the cornea. This part is also important for light refraction and focusing of images onto the retina. The lens can change shape to fine tune focus, change focal distance, and create a sharp image.The vitreous is the clear, thick gel-like substance between the lens and retina. The function of the vitreous gel is to help with optical power, maintain eye structure and retinal health.
It is very clear, 98% water, and doesn’t change from birth, unlike many fluids in the body that are replenished throughout life.The retina is a tissue that lines the inner surface of the eye. It senses light brought through from the cornea, pupil, and lens, and is where the image of the world appears after focusing. The macula is where very fine focus occurs. The macula has inside it the fovea, which has tightly packed cones in it that sense color. All of these parts of the retina can be thought of like the film of a movie or a camera.When light hits the retina, it excites nerves through chemical and electric messages that cause the nerves to function.
These nerve impulses go to parts of the brain that can put the images and colors of the visual world into understandable information. These messages are sent to the brain via the optic nerve, also called the cranial nerve too. It is the last stop before sending information from the visual world to the brain.
The eye has a front and a back part. The front consists of the:
These parts let light information in, focus it, and send it to the back of the eye. Some of these parts, like the sclera, are for protection.
The back of the eye is where light information is further focused. Color is assessed in the retina and sent to the brain via chemical and electrical impulses down the optic nerve. The front and back parts of the eye must work together to allow mammals to see and make sense of the outside world.
The Parts of the Eye
- Iris: the colored part of the eye
- Pupil: the dark circle inside the center of the eye
- Cornea: clear covering over the pupil and iris
- Sclera: the white part of the eye that becomes pink or red
- Conunctiva: the inner layer of skin on the eyelid
- Lens: works with the cornea, important for light refraction and focusing of images onto the retina
- Vitreous: clear, thick gel-like substance between the lens and retina
- Retina: a tissue that lines the inner surface of the eye, where images come together
- Macula: where very fine focus occurs
- Fovea: inside the macula, contains tightly packed cones that sense color
- Optic nerve: sends color information from the retina to the brain
This informative lesson is designed to help you to:
- List the components of the front and the back of the eye
- Discuss the purposes of the eye’s parts